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首页> 外文期刊>Journal of South American earth sciences >Tectonic setting of the Taubate Basin (Southeastern Brazil): Insights from regional seismic profiles and outcrop data
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Tectonic setting of the Taubate Basin (Southeastern Brazil): Insights from regional seismic profiles and outcrop data

机译：陶巴特盆地的构造环境（巴西东南部）：来自区域地震剖面和露头数据的见解

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In southeastern Brazil, a series of onshore Tertiary basins provides good evidence for post-rift tectonic activity. So as better to constrain their tectonic setting, we have revisited outcrops in the Taubate and Resende basins and have reinterpreted 11 seismic profiles of the Taubate Basin. Where Eocene to Oligocene strata crop out, syn-sedimentary faults are common and their senses of slip are mainly normal. In contrast, for two outcrops in particular, where syn-sedimentary faults have put Precambrian crystalline basement against Eocene strata, senses of slip are strongly left-lateral, as well as normal. Thus we distinguish between thin-skinned and thick-skinned faulting. Furthermore, at four outcrops, Precambrian basement has overthrust Tertiary or Quaternary strata. On the seismic profiles, basal strata onlap basement highs. Structures and stratigraphic relationships are not typical of a rift basin. Although normal faults are common, they tend to be steeply dipping, their stratigraphic offsets are small (tens of metres) and the faults do not bound large stratigraphic wedges or tilted blocks. At the edges of the basin, Eocene or Oligocene strata dip basinward, have been subject to exhumation, and in places form gentle anticlines, so that we infer post-Oligocene inversion. We conclude that, after an earlier phase of deformation, probably during the Late Cretaceous, the Taubate Basin formed under left-lateral transtension during the Palaeogene, but was subject to right-lateral transpression during the Neogene. Thus the principal directions of stress varied in time. Because they did so consistently with those of the adjacent regions, as well as those of the Incaic and Quechua phases of Andean orogeny, we argue that the Tertiary basins of southeast Brazil have resulted from reactivation of Precambrian shear zones under plate-wide stress.
机译：在巴西东南部，一系列陆上第三纪盆地为裂谷后的构造活动提供了良好的证据。为了更好地限制其构造环境，我们重新考察了陶巴特和雷森德盆地的露头，并重新解释了陶巴特盆地的11个地震剖面。在始新世至渐新世地层发育的地方，同沉积的断层是常见的，其滑脱感主要是正常的。相比之下，特别是对于两个露头，同沉积的断层使前寒武纪的晶体基底抵御始新世地层，滑移感很强，与正常情况一样。因此，我们区分出薄皮断层和厚皮断层。此外，在四个露头，前寒武纪基底上覆有第三纪或第四纪地层。在地震剖面上，基底层重叠于地下室的高点。构造和地层关系不是裂谷盆地的典型特征。尽管正常断层很常见，但它们往往会陡倾，地层偏移很小（数十米），并且断层不会束缚大的地层楔块或倾斜的块体。在盆地的边缘，始新世或渐新世地层向盆地倾斜，已被发掘出掘，并且在某些地方形成了缓和的背斜，因此我们推断出渐新世反演。我们得出的结论是，在变形的早期阶段之后（可能在白垩纪晚期），陶巴特盆地在古近纪期间在左旋作用下形成，但在新近纪期间经历了右旋作用。因此，应力的主要方向随时间变化。因为它们与相邻区域以及安第斯造山带的印加纪和盖丘亚纪相一致，所以我们认为巴西东南部的第三纪盆地是在板块应力作用下重新激活了前寒武纪剪切带的结果。

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